Permanent magnet material



2,927,898 V PERMANENT MAGNET MATERIAL United States Patent Franz Pawlek, Berlin-Li'chterfelde-West, Germany, as-

signor to Licentia Patent-Verwaltungs-G.m.b.H., Hamburg, Germany Application March 30, 1959, Serial No. 802,814 7 1 Claims. or. 252-525 plication Serial No. 456,070, filed on September 14, 1954,

now abandoned, for Permanent Magnet Material.

It is well recognized that-a satisfactory material for permanent magnets must possess high'remanence and should also, have a high 'coercive. force. At the same time, economic considerations demand that the material be composed of constituents which are not so expensive as to make their use prohibitive. Furthermore 'it is desirable that permanent magnetmaterials be composed of constituents which are readily available. 1

There are certain magnetic materials on themarket, such as"alloys, which' have reasonably good magnetic properties in terms of remanence and coercive force.. However, many of these materials include such metals as oobalt and nickel which are difficult to extract from their lowing:

Other and further objects and advantageous features of the present invention will hereinafter more fully appear in connection with the'drawing which constitutes a triangularplot, in mol percents, of the three-component system of Fe O PhD and SiO As mentionedin the foregoing, the permanently magnetic material according to the present invention can be prepared very inexpensively. The inexpensive nature of the material is attributable to the. easyavailability of its constituents and to the simplicity of the'method of manufacturing the material, as will be'e'xplained in the fol- An aqueous slurry should first be prepared by (1) pulve'riiing metallic oxides of the type and in the proportions falling within the pentagon defined in the foregoing, and (2) mixing the resultingpowder with water.

The water is then filtered 01f, and the remaining solid dried by applying moderate heat. In order, to facilitate the subsequent molding steps and the removal of the magnetic material from the molds, a small amount of parafiin, dissolved in trichlor'oethylene, may at this time be added to the mixture to act as a lubricant. Alternatively, stearic acid "of 'othersuitable waxes may be employed for the same purpose.

Following the addition of the lubricant, the mixture will be dried again, permitting the solvent of the lubricant'to evaporate. The powdered mixture should then be pressed into molds of any desired shape, whereupon ores and which, in times of emergency, are considered strategic materials to be reserved primarily for strategic V goods.

sonable prices, but which do not possess the abovei mentioned magnetic characteristics to the desired degree. Therefore, any material which is characterized, at the same time, by ready availability, low cost, and favorable the present store of engineering achievements.

Accordingly, it is an object of the present invention to magnetic properties constitutes a very valuable addition to provide a permanently magnetic material which is characterized by high values of remanence and coercive force and which, at the same time, is composed of inexpensive and readily available constituents.

It is another object of the'invention to provide a reasonably simple and convenient method of producing the material mentioned above.

It is a further object of this invention to heat a mixture of Fe O PhD, and SiO said mixture forming a three component system the proportions of which are represented in mol percent in an equilateral triangle, whereby the composition of the mixture is defined by a pentagon inside said triangle, said pentagon having the following corners or coordinates in mol percents:

65 of FezOs 30 of PhD 5 of S10 75 of F6203 20 of PM) 5 of S102 81 of FezOr 15 of PbO 4 of S10: 84.5 of F620: 15 of Pb 0.5 of S10: 76 of FeZO; 23.5 of PhD 0.5 of $102 the pressed material will 'befired in' an air current. for a period of between three and four hoursat a temperature between .700 and 1,200" C. Finally; the pressed material is cooled and removed from the'inol'ds.

While it will be understood that the magnetic characteristics of :the finished magnetic material depend somewhat upon ther percentage of the various constituents used informulating the material, I have'found that suitable mlxture. ratios .are the following: e

a. Rema- Coercive w R10 PbO SiO: hence in Force in Gauss Oersted 1. M01 percen 65 g 30 s 1, 330 1, 650 2. M01 percent.-- v .20 6 1,410 3, 200 3. Molpercent.-. :81 15 4 1,000 3,500 4. Molpereent.---. 84.5 15 0.5 1, 300 2,100 5. M01 percent--- 1 74 25 1 1,400 ,900 6. Molpercent. 12,45 3,85 g? 1,700 1,850 7. M01 percen 77 20 3 1,800 2, 250 8.. Mol percent. 78. 63 19. 15 2. 22 2, 000 2, 9. Molpereent 81.65 10.4 I 1.05 1,600 2, 000

Referring to the drawing it willbe evident that the first four examples represent the coordinates at four corners of the pentagon indicated by the reference numerals 1 to 4, respectively; the last five examples lie within the pentagon. The best results are obtained with the composition of Example 8.

Regardless of remanence, the following compositions render high coercive. forces:

65-80 mol percent of Fe O 20-30 mol percent of PbO 1-5 mol percent of SiO i'I'hese mixtures are to be fired preferably for four hours at a sintering temperature of l,000 vC. in a current of air and should be cooled thereafter.

The resistivity: of the magnetic materials thus formed was found 'to be in the range of 10 9 ohm-cm.

It will be noted that the above-described characteristics show a significant improvement over the known types of permanently magnetic materials. In addition, the new method of making the material is simple and depends only upon inexpensive and easily available constituents,

Furthermore; the-property known as the B H' factor (the product-obtained by multiplyingnthe magnetizing field.

strength by the resulting magnetic-flux density) is extremely high for the new material. The B-H product or factor for a given material. often isof; values-as. a

criterion for use in selecting a permanently magnetic material;

While-I have described myinvention' in connection with specific compositions and exarnples ofthenew method, I wiSh'it-r to be understood that other andfurthermodifications, apart'fr'om th'ose shown or suggestedlherein, may be employedwithout departing'from the. spirit andscope of my invention; which maybe defined by, the-appended claims.

What is: claimed is:

1. A permanently magnetic material prepared by, hea 7 ingamixture of Fe PbO, andSiO to a:temperature between 700 and 1,200 C., said mixture fallingswithin the bounds of a pentagon defined onan equilateral tri' angular plot of the the three components of the-mixture, each side of the triangular-plotrepresentingone of the components in mol percent from 0 to 100%, the pentagon being represented b'y'the following coordinates:

I Feaoa PhD 810 65 I 3O 5': 75 2O 5..

2. A permanentlymagneticmaterial preparedby heate ing a mixture of 65 to 80 mol percent of F'e O to 30 mol percent'oflPbO, and approximately 1 toS mol percent of $0; to a temperature between 700 to 1,200? C. r

3. Amethod of producinga permanently magnetic material comprising the steps of preparing a mixture in the three-component systems Fe O -PbO--SiO defined within a pentagon having as corners on an equilateral triangular. plot the. following coordinate ,moL percentages:

Fegoa 510:

q -10: mi cncn ppncncmol:

5f and'of heating said mixture between 700 and L200 C and cooling 1 themproduct. thus obtained. 7

4. A method according to claim 3, characterized in that the mixing ingredients are pulverized and converted into: an aqueous suspension and that the heating is carried outin air current for three to four hours.

5. A method for producing a permamently magnetic material comprising the steps of'rnixing to mol'percent of Fe' O},

1 m5: mol :percent: ofzSiQg approximately Referencescited in the fileeofiv this patent UNITED STATES PATENTS 1',82'1',208I Dahlberg, S'ept.' 1,'193'1 2J62TZ77 Went et a1 Sept. 11, 1956 FOREIGN PATENTS 697,219 Great Britain Sept." 1'6, 1953 OTHER REFERENCES a Harvey et al.: RCAiReview,.September. 1950, page 346. Went et-ah: PhysicaLReview, vol. 86, pages 424425 (1952). V V 

2. A PERMENENTLY MAGNETIC MATERIAL PREPARED BY HEATING A MIXTURE OF 65 TO 80 MOL PERCENT OF FE2O3, 20 TO 30 MOL PERCENT OF PHBO, AND APPROXIMATELY 1 TO 5 MOL PERCENT OF SIO2 TO A TEMPERATURE BETWEEN 700* TO 1,200*C. 